The concept of chocolate producers having to acquire machines to clean cocoa beans before use is a concept I am unable to comprehend. If you are buying beans that require cleaning, you are not only wasting chocolate production time but also paying premium prices for trash. Buy beans that are properly processed and forget about trying to compensate for shoddy quality control at the producer level.
The final stage of our process exposes all beans to a cleaning phase that removes all material that is not useable bean. In addition our machinery separates beans by size (mass) and offers uniform, clean beans that can go directly from the sack to the roaster.
Forget about adding a process to the already complicated issue of chocolate and buy from producers that include practice quality control in the process line .
The cleaner in the video could be adapted for winnowing, not cleaning prior to roasting. It's a device that could be more functional than one made from PVC pipe. Using pre-classification sieves before winnowing would improve throughput and yield.
You are right, there should be absolutely no need for the purchaser of cacao beans to clean cocoa beans. However, not all growers/exporters are as diligent as you are, and not all purchasers understand the cost/labor tradeoff. It makes more sense to pay a premium for cleaned beans because the farm gate premium is almost always going to be far less than the cost of doing it yourself.
Unfortunately, quality control with respect to cleaning and inspection for defects is not always done on the farm. I purchased some beans from the DR through a broker and the official grading specification allowed up to 3% trash -small pieces of wood, flats, doubles, and other defects - by weight. I have seen bags with nails and stones in them.
Some countries are exporting with 25% trash. Do this long enough, and you'll find everything you can imagine (and things you wouldn't have imagined) in cocoa beans.
Long term planning and critical thinking are not strong in all parts of the world - especially when you may not know where you're going to get the money to buy dinner tonight. As a result, short term financial decisions are often made - such as "if i put rocks in this bag, it weighs more and i'll get more money today". In actuality, while this is true for today, what it means is that they're shooting themselves in the foot for tomorrow - as folks will catch on to the fact that they're not buying what they think they're buying. That said, if i don't eat today, i don't care much about tomorrow.
A fundamental shift across multiple origins around incenting quality at the grower AND exporter level is needed to change the mindset. It's incredibly difficult, and I don't believe it'll occur on a large scale quickly.